The long range objectives of this research program are to define the molecular and cellular processes underlying animal learning and memory. In Drosophila, the dunce gene is the best characterized of the set of genes involved in olfactory learning and memory, causing an abbreviated memory when mutated. Recent work has demonstrated that the product of dunce, cAMP phosphodiesterase, is particularly concentrated in mushroom bodies, a collection of about 2500 neurons and their associated neuropil in each brain hemisphere. This observation along with several others, led to the development of a new model envisioning mushroom body cells as the primary cells serving olfactory learning and memory and those cells which require the dunce gene product for their normal physiology in this role. The proposed research will test whether the expression of dunce in mushroom body cells is sufficient for normal learning and memory. Flies carrying chromosomal rearrangements which preserve or delete the specific dunce promoter (one of several) responsible for mushroom body expression will be tested for normal olfactory learning/memory, to determine whether behavioral abnormalities correlate with the loss of this promoter. And, the enhancer/promoter elements responsible for normal mushroom body expression of dunce and other mushroom body-specific genes will be defined and used to drive dunce minigenes in transgenic flies, to determine whether this expression is sufficient for rescue of dnc mutation. Other experiments will determine whether dunce activity is required physiologically or developmentally for normal learning and memory. Transgenic lines, carrying a dunce minigene driven by the hsp70 promoter which appears to rescue dnc mutants, will be used to determine when during development and/or adulthood that heat shock is required to effect rescue. In addition, temperature-sensitive alleles of dnc will be isolated and used to define the phenocritical period for dunce activity. Finally, mushroom body-specific enhancer/promoter elements will be used to promote the expression of a temperature-sensitive toxin gene in mushroom bodies, to determine whether the cells are required for learning and whether they are required for the long-term storage of information after training. These experiments will enhance our understanding of learning and memory in Drosophila, specifically providing evidence for when the activity of "learning and memory" genes is required and whether mushroom bodies are indeed, the true neuroanatomical substrate for olfactory learning and memory.